Apparatus for illuminating components of transparent material used in the inspection for defects.

p0001The present invention relates to a device according to the preamble of claim 1.

p0002Components made of transparent material, for example, optical or ophthalmic lenses must be tested prior to use for errors, particularly surface defects such as scratches, wiper, cracks, dig, stains, etc. and for inclusions such as bubbles or streaks. Such errors would reduce the usability of a lens if they exceed the specified in DIN 3140 limits.

p0003Typically, the testing of optical components is carried out as a visual inspection by humans. Such an assessment must be carried out in a largely darkened room. It is expensive, not reliable enough not sufficiently objective and because of the high monotony of testing procedures.

p0004It has therefore endeavored to develop methods and devices for automatic, objective testing of optical components.

p0005From DE-OS 32 37 511 it is known to bring test optical components in the optical beam path of a television camera and through the component a test pattern imaged on the camera. The induced errors in the component faults lead to a video signal from said through the component did not affect nominal signal deviates. From the deviation from the desired and actual signal is closed to the error. An operating according to this method apparatus is quite complicated and can minor faults, not to recognize, for example, by scratches, wiper or hairline cracks.

p0006The sensitivity of the test procedure is to increase proposed in DE-OS 30 11 014 to illuminate the component to be tested as a whole, to produce a television image and to analyze the video signal line by line. This method is cumbersome, expensive and not sufficiently precise.

p0007An even older proposal for a test method can be found in DE-OS 23 37 597. There, a light beam is focused onto the surface of the component to be tested and is point-like moves while maintaining its focus state on the surface. The Trough the component passing light is reflected back, occurs again through the component and then falls onto a detector. Variations in the intensity of the signal receiver allow an error to close and to locate these also.

p0008An operating according to this method is very expensive device. It only allows the examination of the surface of the workpiece to which the scanning beam is focused. The illumination of the object to be tested is carried out here by the fact that the specimen is rotated about its axis and the incident light beam is deflected slowly radially so as a spiral pattern describes on the specimen, with its focus state must be continuously adjusted according to the curvature of the surface to be scanned ,

p0009It is to provide a device for illuminating the components of transparent material in the check for surface defects and inclusions, which allows the object of the present invention, regardless of its form always illuminate the component and thereby generate a light distribution throughout the component volume which allows interfering signals from arbitrarily selectable thickness levels, in particular to evaluate from both surfaces of the component. The actual evaluation is performed by a downstream measuring device which can be constructed in various ways, for example, according to the proposal of the German Patent Application P .. .. ... the Applicant, entitled "Apparatus for testing components of transparent material for surface defects and inclusions "having the same filing date as that of the present application.

p0010This object is achieved by a device, whose structure is indicated in the characterizing part of claim 1.

p0011In the inventive apparatus, a light beam generated by the light source that can be focused with great depth of field. For focusing the light beam is a, preferably designed as a f-theta lens converging lens. A focal point of this lens is located in the fulcrum of the scanner, so that the rotary motion of the deflected light beam from the scanner is converted to a parallel displacement behind the lens. In order for the component to be tested is illuminated with a light beam that moves parallel along a diameter of the rotating component, thereby creating a light band. This spoke-shaped band of light travels during the rotation of the component by 360 ° once the component and thus illuminates every volume even with light about the same focus state.

p0012Of any errors in the surfaces or inside the component disturbed in their normal spread of radiation is detected in the checking device downstream.

p0013Is it in the components to be tested, for example, lenses with highly curved surfaces, so it is possible that the light band is no longer detected both lens surfaces in a graded for less curved lenses position of parts of the lighting system. For this reason an adjustable tilting mirror is arranged between the collecting lens and the component to be tested. With the help of this mirror, it is possible that the illumination system to adapt to all circumstances of the component to be tested, ie, the angle of impact and point of impact of the scanning light beam to be so selected that both surfaces are thus illuminates the entire volume of the component.

p0014Claims 2 and 3 relate to an advantageous embodiment of the light source; Claims 4 and 5 to an advantageous development of the scanner. The appropriate storage of the tilting mirror is subject matter of claim 7. The claims 8 and 9 describe advantageous embodiments of the illumination device of the invention.

p0015The invention is described below with reference to Figures 1 to 4 of the accompanying drawings. In detail:<ul><li>Figure 1 shows an embodiment of the lighting device according to the invention in a schematic representation.</li><li>Fig. 2 is a plan view of the component to be tested the Fig. 1;</li><li>Figure 3 shows the conditions when illuminating a biconvex lens with highly curved surfaces. </li><li>Fig. 4 shows the conditions when illuminating a plano-concave lens with strongly curved concave surface.</li></ul>

p0016In Fig. 1, (1) a laser referred to, which is preferably formed as a He-Ne laser, and operates at an operating wavelength of 628 nm. In this laser, a mode filter (2) is arranged. The light passing through this filter parallel beam of light (19) meets at the point (11) on a polygon mirror (3), which by means of a motor (12) is rotated in the arrow direction. Characterized the light beam (19) between the extreme positions indicated with (19a) and (19b) is periodically deflected. The from the mirror (3) reflected light beam (19) passes through a converging lens (4), which is advantageously designed as a f-theta lens. The focal point of this lens is coincident with the pivot point (11) of the deflecting polygon mirror. Behind the lens (4) extend the deflected light beam (19a) and (19b) parallel to each other. They are prepared by a deflection mirror (5) is deflected on the lens to be tested (6). The deflection mirror (5) is a motor in the direction of arrow (16) slidably and in the direction of arrow (17) rotatably.

p0017The lens to be tested (6) is arranged on a turntable (7) which via a gear wheel (9) by a step motor (8) is rotated. The stepping motor (8) and the motor (12) for rotation of the polygon mirror (3) are synchronized via an electronic arrangement (13).

p0018By the illustrated illumination system, as Fig. 2 shows the lens (6) in the form of a narrow band of light (14) illuminates, the the light beam (19) between its extreme positions (19a) and (19b) are crossed. At the same time the lens (6) by means of the stepping motor (8) is rotated in the direction of arrow (15), so that after a full rotation of the lens (6), the spoke-shaped band of light (14) is completely migrated through the lens, that is full during an round through 360 ° to be illuminated all the volume elements of the lens (6). The lighting takes place by means of the deflected light beam (19) attached to both surfaces of the lens (6) has approximately the same focus state.

p0019In the light direction seen behind the lens to be examined (6) is a schematically illustrated testing device (10) is arranged, which receives the through the lens (6) passing light and which consists of an irregular interference of light, for example, by one of the surfaces of the lens (6 detected), faults and isolated.

p0020seen in light direction in front of the lens (6), an adjustable slit diaphragm (18) is arranged, which limits the spoke-shaped band of light (14). The deflection of the light beam (19) is made such that it would take in the extreme position (19b) on the support (7). To avoid disruptive reflections then serves the slit diaphragm (18).

p0021In Fig. 3, the test lens (20) is designated. It is designed here as a bi-convex positive lens with highly curved surfaces. Due to this shape of the lens surfaces at a would, for example for examination of the lens (6) of Fig. 1 serving location (5a) of the reflecting mirror (5) light does not illuminate the entire volume of the lens (20). For this reason, the reflecting mirror (5) is displaced in the direction of arrow (21) and rotated in the direction of the arrow (22) and reaches the position (5b). In this position, the laser (1) is deflected produced light beam (19) between the extreme positions (23a) and (23b). It is evident that this band of light now recorded both surfaces of the lens (20) evenly.

p0022Similar conditions are obtained in the examination of a lens (24) of Fig. 4. The illustrated there plano lens has a strongly curved concave surface and in the normal position (5a) of the deflection mirror (5) would not illuminate the entire lens volume. For this reason, here the mirror (5) is displaced in the direction of arrow (21) and rotated until it reaches the position (5b) in the direction of arrow (22). In this position the light beam (19) between the extreme positions (25a) and (25b) is deflected. It is evident that now the entire volume of the lens (24) is uniformly illuminated.